The present invention relates to an improved snare mechanism for a drum and more particularly relates to an improvement in arrangement of a snare mechanism on a drum which exhibits special acoustic effect by selective contact of a snappy with a drum head.
A snare mechanism for a drum is usually provided facing a rear side drum head, with a snappy made of several fine metallic wires. When the snappy is placed in contact with the rear side drum head, vibration of the rear side drum head is transmitted to the snappy to cause special acoustic effects in which musical tones of lilting tone colours are generated. When the snappy is moved out of contact with the rear side drum head, thick musical tones are generated. Thus, by moving the snappy into and out of contact with the rear side drum head enables generation of musical tones of different tone colours.
In the case of the conventional snare mechanism, however, movement of the snappy into and out of contact with the drum head is caused by vertical movement of snappy plates or by pulling the snappy plates. Such a mechanism allows a very narrow range of adjustment in height and tension of the snappy and, as a consequence, cannot provide satisfactory effects.
When the front side drum head is beaten, vibration caused thereby is transmitted to the rear side drum head via the air column in the stem of the drum, and a corresponding vibration of the rear side drum head drives the snappy for vibration. Such a generating mechanism of vibration results in poor rising characteristics of the tones to be ultimately generated.
During transmission of vibration from the front side to the rear side drum head, tones of high frequencies tend to experience early decay due to viscous resistance of the air column in the stem of the drum. Because of such early decay it is difficult to obtain tones of rich tone volume over the entire tone range.
When the snappy is pressed against the drum head, the driving force must act against a component of force caused by tension of the drum head. There is a linear relationship between the distance of movement of the snappy and the load from the drum head (the above-described component of force). However, this linear relationship is lost near the maximum moving distance of the snappy.
To lift the snappy, a link mechanism is conventionally employed. This link mechanism takes the form of a crank which includes an upper lever coupled at its top end to the snappy and a lower lever coupled at its lower end to a driving source, and the two levers are pin-jointed at their mating ends. When the angular speed .omega. of the levers is assumed to be constant, the relationship between the rotation angle .theta. of the lower lever and the driving force F given by the link mechanism is defined by the following equation. EQU F=m.gamma.(cos .theta.+.gamma./l cos 2.theta.).omega..sup.2
Wherein m indicates the equivalent weight of the link mechanism.
It will be well understood that the rotation angle .theta. varies in the range from 0 to 45 degrees. When the angle .theta. is equal to 45 degrees, the direction of the upper lever is normal to that of the lower lever and, under this condition, the lifting stroke is at its lower end. When the angle .theta. is equal to 0 degree, the direction of the upper lever coincides with that of the lower lever and, under this condition, the lifting stroke is at its top end. As is clear from the above-described equation, the value of the driving force F created by the lifting mechanism decreases as the angle .theta. approaches 0 degree, in other words, as the lifting stroke approaches its top end. Thus, the snappy cannot contact the drum head with a constant driving force over the entire range of the lifting stroke of the lifting mechanism. In addition, the dynamic characteristics of the lifting mechanism is rigidly defined by its construction, thereby disenabling free output of the driving force.